The Methodology of Melioration and Restoration of the Largest Dumps of the Most Coal Basin

Reclamations of dumps in the Most Basin that is located in the North Bohemia consist of restoration of extremely unfavourable properties of rocks that are poured down onto the dump body. These rocks come from the surface layer and the layer where coal bed is present. Sands, clay sands and kaolin (illitic clays) are the main components that occur in the material. Other components are predominantly organic (coal) mass, siderite and pyrite. This report briefly summarizes the history and present of ore, non-metallic and coal mining in the region and addresses in detail the issue of moderating the consequences of mining, which is one of the principal activities of the Research Institute for Brown Coal, j.s.c. in Most. The concept of landscape reclamation in the largest dumps after mining ends, the technical reclamation methodology and the well considered use of fertilizable soil are main results presented in this article.


Introduction
The area of interest lies on the border of the oceanic and continental climate. For the basin part of the area is a characteristic the inverse states where the cold air and low-laid clouds capture the sun's radiation (especially in winter). Due to rainfall shadow that is caused by the Ore Mountains, the basin has lower cloudiness, low rainfall, and higher temperature fluctuations, closer to the continen-DOI: 10.4236/jep.2017. 813097 1584 Journal of Environmental Protection tal climate, while the mountainous areas are defined by ocean climate [1]. The North-Bohemian Basin area is known for its largest Czech brown coal deposit.
Over 70% brown coal reserves are currently being extracted in the Most Basin.
The opencast quarries caused extensive damage to the landscape. Reclamation works became significant in order to restore the newly created anthropogenic formations and integrate them into the surrounding environment. The rocks that are poured down onto the dump body are mechanically unstable with respect to wind and water erosion and during weathering they develop an unfavourable, phytotoxic nature, due to the influence of SO 3

History and Present of Non-Coal Mining in the Region
There were three large ore districts in the North-Western Bohemia region. Jachymov, as the most important, used to be a great deposit of Ag-Bi-Co-Ni formation. Silver extraction culminated in the 16 th century. Silver Jachymov thalers have given the name to the American dollar. After exhausting silver mineralization, nonferrous metals were extracted at the site, followed by uranium ore in the last phase. Today Jachymov belongs among leading Czech spas. Krupka was the oldest ore deposit of Sn-Cu-Mo formation already known in the 13 th century.

History and Present of Coal Mining and Reclamation in the Region
The history of coal mining in the region spans hundreds of years. The records in the chronicles from the 14 th -15 th century are the proof. At the turn of the 19 th -20 th century dozens of deep mines were extracting here, and first small opencast mines started to appear. With such a concentration of mining the North-Western Bohemia has obviously gone down in the history of reclamation, too. These started not only in the North Bohemian Basin but in whole of Bohemia in the year 1908 when a reclamation agency of the municipal agricultural council was established in Duchcov. According to the data of this body 448 ha of total 3372 ha devastated land was reclaimed in the entire district at that time. It mainly concerned smaller areas corresponding to the mining dimensions of that time. Reclamation took place, even later, in a simple undemanding way by the Journal of Environmental Protection recovery of a former field and its cultivation. After the 2 nd World War the significance of deep mines gradually decreases and mining starts to be concentrated in small opencast mines. The systematic development of reclamation work takes place in the fifties. In the year 1957, an agricultural and reclamation plant SHD was established in Teplice. The first Reclamation Master Plan was prepared in Mining Projects Teplice in 1959. Reclamation work was provided by the national enterprise North-Bohemian Brown Coal District-Rekultivace in Teplice, Mining Constructions Most and later Reclamation constructions Most which has gradually changed into an investor-supplier organization. Most of the reclamation in the district was carried out with the fellowship of research institutes and Mining Projects Teplice. More demanding technical adaptations were not provided until the sixties. Most of the time, the consequences of old underground mining and the sporadic excavator dumps of small mines were being liquidated. Species of reclamation trees were planted. In the seventies, coal mining gradually became concentrated in several large opencast mines. Each year the areas abandoned due to mining which were gradually reclaimed increased in number. The field was treated before the biological reclamation, fertilizable soil was brought in and the area was drained. Brown coal mining culminated in the eighties, when the annual extracted volumes exceeded 70 million tonnes. Thus reclamation gained a new dimension. Vast areas of dumps were handed over for reclamation, reclamation of high dump bodies became a new issue. In that time selective mining and depositing of soil usable for reclamation was launched. The changes were reflected in the technology with which reclamation work was performed.
After the transfer to market economy in the beginning of nineties of the last century the annual, the extraction of brown coal gradually decreased to today's cca 40 million tonnes. Mining was concentrated in four large opencast mines: Libous, Bilina, Vrsany and CSA owned by the mining company North-Bohemian mines, a.s. and Most Coal Company, a.s.. The mine Bilina became the largest opencast mine of the region and the Czech Republic with a cca 5 km coal face length, cca 200 m upper bed thickness and cca 30 m coal seam thickness. At this time,, the reclamation technique and philosophy underwent a quality development. The dump construction is controlled to enable successful reclamation and classification of soil, and its selective depositing has been introduced. Many failed reclamations provided lessons for learning, e.g. Strimice dump reclamation where several new plantings died. Since then the thought-out adaptations of dump surfaces, based on the results and recommendations of the research work, have been taking place. Mining models have been prepared emphasizing wider landscape enhancement concepts of large areas with a connection to the existing ecosystems, but also the planned economic and social structures of the area. That is the example of vast dumps Strimice, Pokrok and Radovesice reclamation. The reclamation plans also include the creation of large bodies of water in the closed down mines. Totally new landscape elements should be formedin this way, with an impact on the environment, and they will still have to be analysed in detail. The first phase of the reclamation work, under the North Bohemian Journal of Environmental Protection Basin conditions, includes the adjustment of the rock environment in the top horizon of the reclamation sites using locally available fertilizable rocks. Scientific biological reclamation focused on the future use of landscape then follows. The success of reclamation work is, to wide extent, dependent on the knowledge of the properties of the overburden rocks from the opencast mines, the research of top horizon in the dump, scientific use of the fertilizable rocks and preparation of a suitable reclamation methodology. The Research Institute of Brown Coal, a.s. deals with this issue and some of the results have been presented in this report. The total status of the area of interest is shown in Figure 1.

Properties of the Coal Seam in the Most Basin
The  Table 1.
Loess, loess loams and gravel sands are perfect for reclamation, but a mixture of clays makes them rather good for reclamation. Sandy clays, sands and yellow clays have poor restoration usability. The upper horizon is formed by phytotoxic rocks with a mixture of coal and cannot be used for reclamation. The reclamation of opencast mines, internal dumps and the most important external

Strimice Dump Restoration
The The middle layer's soil reaction is lightly alkaline with increasing calcite content.
The nitrogen and humus content is low. The nutrient content is increasing slightly against the upper layer. Grain size of both layers is defined as lightly coarse. Predominantly bentonites were used for soil fertilization. The results prove the success of the method selected for the Střimice dump reclamation. It is shown in Table 2. Given the current market price of bentonite, it is not practically possible to employ this type of reclamation today.
Completed reclamation of the Strimice dump is shown in the Figure 3. There is an airport with a surface of approximately 90 ha that is surrounded by agricultural reclamation. The slopes of the dump, where the forestry reclamation was made, now serve as a recreational area with tourist trails.

Radovesice Dump Restoration
In 1964 the reclamation of Radovesice dump (50.5582708N, 13.8002164E) began. It is the largest dump in the Czech Republic [7]. Given the size of the dump, and its significance and severe character of the most deposited overburden rocks, there has been an adaptation of the dump surface performed using local   Table 3.
After the completed technical reclamation the biological, mostly forestry reclamation is now being done in the area. A suburban park, serving the needs of the citizens of Bilina, will be built in a part of the area. A newly created anthropogenic soil profile is shown in Figure 4.

Restoration of the Bilina Mine's Inner Dump
Most volumes of the extracted overburden rocks of the Bilina mine (50.5695406N,   Table 4.
Only loess and loess loams from the mine forefront is used for the reclamation of the Bilina mine. After the soil profile modification ends, forestry and agricultural reclamation will be performed in the dump. After the completion of the hydrological reclamation in the mine and the mine lake formation, beaches and other recreational spaces for the Bilina citizens's recreation will be created in the off-shore parts of the dump.

Conclusion
The report is concentrated on the history, present and perspective of mining and reclamation in the north-western bohemia region. Reclamation work has been developing based on the extent of coal mining, and now maximum attention is